Combination spark plug and fuel injector



Jan.;l8,-- 1949. H. 'RABEZZANA arm.

COMBINATION SPARK PLUG AND FUEL INJECTOR 2 Sheets-Sheet 1 Fil ed May 27, 1944 A 29 INVENTORS 3&2 @Jezzeze I .Z'vwcx'r M 'ITORNEYS COMBINATION SPARK PLUG AND FUEL IfiJECTOR 3nven'tor:

Patented Jan. 18, 1949 COMBINATION SPARK poratlon of Delaware PLUG AND FUEL CTOR Hector Rabezxana, Flint, Micln, and Francis J.

Wiegand, ltldgewood, N. 1., assignors to General Motors Corporation, Detroit, Micln, a cor- Application May 27, 1944, Serial No. 537,002

Supplying fuel to internal combustion engines by injection possesses the advantages over carbureticn of greater economy and more even distribution of fuel together with less sensitivity and consequently less likelihood of improper ad-- justment and poor functioning. There is also no possibility of backfire, nor is there any problem of ice formation because there is no evaporation of fuel except in the combustion chamber. Fuel injection also makes it possible to use lower grade fuel than is required for carburetion.

When fuel injection is employed it is customary to provide a separate injector for each cylinder. This requires an additional hole in the head of the cylinder with consequent reduction in cooling area and aggravation of the critical problem of cooling the cylinder head. In the case of liquid cooled engines it is especially diflicult to find a place for the injectors because of the water jacketing.

We have found that all of the advantages of fuel injection may be obtained without the recited disadvantage by combining the fuel injector with one of the spark plugs. The combined unit may be substituted for one of the usual plugs so that no change is required in the cylinder head,

Extensive tests of the invention have revealed that a number of important advantages are obtained in performance of the spark plug. Thus, the fuel circulating throughout the plug and passing into the combustion chamber through the valved passage provided in the center electrode cools the insulator, permitting the use of a longer insulator skirt projecting into the combustion chamber so that the plug is practically free from fouling by material, such as lead, which is deposited on the insulator during the operation of the engine. The fuel also cools the center electrode thereby greatly reducing the erosion caused by the sparks and increasing the life of the electrode.

According to our invention the interior of the spark plug shell is filled with fuel under pressure so that in effect the insulator is submerged in fuel. With this arrangement the fuel serves as a liquid seal in series with the seals normally provided to prevent passage of combustion chamber gases between the insulator and the shell or between the insulator and the center electrode. Should any leakage develop, the result would only be to cause small quantities of fuel to seep into the combustion chamber and possibly produce incom- 15 Claims. (ill. 123-469) 2 the plug, charring the wiring and sometimes resulting in fire.

Spark plugs are sometimes short-circuited by passage of current around the upper end of the insulator instead of between the electrodes. Since the dielectric strength of the fuel is greater than that of air the resistance to such leakage of current is greatly increased and the possibility of such short-circuiting is greatly reduced. As a consequence it has been found possible to operate the plug with much wider spark gaps. For example, our improved plugs have operated satisfactorily with spark gaps as wide as .050" as compared with a maximum of approximately .012" in the case of conventional plugs. As a consequence, adjustment of the spark gap is less frequently required.

The spark plug herein described is especially designed for use in airplane engines used in combat. In such use it is especially desirable that the construction'be such that while the plug can be readily disconnected from the fuel supply, removed from the engine and replaced, it cannot readily be taken apart and repaired. Attempts at disassembly and repair under adverse conditions in the field are likely to result in improper assembly with resulting leakage of gasoline or failure or the plug.

Our improved plug is a permanently sealed unit having a simple leak-proof connection with the fuel supply at the and remote from the combustion chamber. It comprises essentially a housing within the lower end of which is arranged an insulator having a central bore containing a hcilow electrode within which is located a pressure operated injector valve. The insulator is held in sealing engagement with a seat provided in the lower end of the housing by suitable means such as a stiff spring. At the upper end of the housing, connection is made with the fuel supply. This connection is preferably made through passages provided in the periphery of the housing so as to permit the usual axial connection of the plete combustion. With conventional spark plugs the leakage of combustion chamber gases past the insulator frequently causes short-circuiting of leads.

There is preferably provided within the upper end of the housing a second insulator having a central bore containing an electrode in conducting relation with the central electrode of the primary insulator. In the second electrode there 3 tion of Taine G. McDougal et al., Serial No. 488,114, filed May 24,1943.

In the preferred embodiment the second insulator is in sealing engagement with a seat provided in the housing and the same spring means that holds the primary insulator on its seat preferably also holds the upper insulator in place.

The housing is preferably formed in two telescoping parts. With an insulator assembled in each part the two parts are assembled under heavy pressure and secured and sealed by welding or soldering to make a permanent assembly.

Plugs of the above description have proven to be very durable, withstanding hundreds of hours of use. They are also readily removed and replaced. No trouble has been experienced from leakage of gasoline. They afford a ready means to convert existing engines to fuel injection. They will'also be found useful where it is desired to inject other materials such as water and alcohol mixtures, decarbonized compounds, or special fuels for short periods of time.

Certain features of construction may find use in spark plugs not adapted for fuel injection, as pointed out in the appended claims.

In the drawings:

Figure 1 is a longitudinal section through the improved spark plug.

Figure 2 is a perspective view of the upper seallng gasket.

Figure 3 is a section on line 3-3 of Figure 1.

Figure 4 is a longitudinal section through a modified form of the invention.

Figure 5 is a section on line 5-5 of Figure 4.

In the drawings, l0 indicates the spark plug housing consisting of a lower shell I! and an upper shell l4 telescoped together under heavy pressure, as hereinafter described, and welded or soldered together as indicated at Hi to provide a substantially permanent assembly.

Within the lower shell is arranged the lower insulator I8 having a central bore 20 enlarged at its upper end to provide a pocket 22. The insulator l8 rests on a copper gasket 24 engaging a cooperating seat formed on the lower shell l2. This provides a liquid and gas-tight seal. Other known forms of seal may be employed if preferred. Within the bore 20 is arranged the hollow central electrode 28 provided at its lower end with a flange 30. Between the flange 30 and the lower end of the insulator I8 is provided a suitable gasket 3| to provide a leak-proof joint. The upper end of the electrode 26 is threaded and is encircled with spring washers 32 of the Belleville type and engaged by nut 34 which, when turned down, locks the electrode to the insulator. A fiat washer, indicated at 36, is preferably arranged between the lower spring washer 32 and the insulator to distribute the stresses.

Cooperating with the lower end of the central electrode 28 is the usual side electrode in the form of a disc 38 welded to the lower end of the shell l2 and provided with inwardly projecting electrode portions, as shown, spaced from the central electrode to provide the usual spark gaps. The width of the gap may be varied by bending the projecting portions of the side electrode. 4

Within the hollow central electrode 26 is slidably fitted the injector valve 40, the lower end of which is normally in sealing engagement with a seat provided on the lower end of the central electrode 26. The stem .of the valve 40 is fluted. as shown. to permit passage of fuel and the fluting is preferably spiral in form to give a whirling motion to the fuel injected into the engine.

The upper end of valve 40 is provided with an annular groove 39 adapted to receive keys 4i. each in the form of half an annulus, fitting in the groove and in a pocket provided in the enlarged upper end of sleeve 42 surrounding the stem of the valve 40. Spring 44 resting on nut 34 engages the enlarged portion of the sleeve 42 and yieldingly holds the valve 40 in closed position, as shown. Nut 34 may be provided with an annular flange 46 to house and center spring 44. This spring is designed to apply relatively heavy pressure, for example 500 pounds per square inch, so that the valve 40 will be opened automatically only when pressures in excess of that amount are applied by a suitable fuel pump, not shown, to the column of fuel back of the valve. In one embodiment, a pressure of approximately 1,000 pounds per square inch at the pump was required to provide the desired pressure at the valve, the remainder being absorbed in losses in the fuel line. It will be understood, of course, that there is associated with the fuel pump a suitable distributor to supply impulses to each of the fuel injectors in sequence at the proper time in the engine cycle.

Within the upper shell i4 is provided a second insulator 48 having an annular shoulder in sealing engagement with an annular seat in the shell as shown, with the usual copper washer interposed at 50 to provide a leak-proof seal. Insulator 48 is-provided with a central bore 52 enlarged at its upper and lower ends. Within the reduced portion of the bore there is arranged a composite central electrode consisting of upper and lower metal contacts or fittings 54 and 56 between which there are interposed a lower conducting glass seal 58, a resistance 60 and an upper conducting glass seal 62, the seals and the resistance may be of the construction disclosed and claimed in said McDougal et al. application Serial No. 488,114. The lower fitting 54 is in electrically conducting relation with the central electrode and injector valve assembly through a relatively weak spring 64. preferably of berylliumcopper alloy. The upper end of the composite electrode of the upper insulator is, through any suitable means such as spring 51. in conducting relation with the ignition lead wire 66 provided with the usual metallic shield 68.

To hold the upper and lower insulators in engagement with their respective seats in the upper and lower shells there is provided an annular spring 10 of C-shaped cross section between which and the upper insulator 48 is arranged a radially slotted washer 12, best shown in Figure 3, and

plain washers indicated at 14. similar plain washers 18 are provided between the lower end of the O-spring l0 and a shoulder provided within the pocket 22 of the lower insulator.

With the parts assembled in the upper and lower shells, as shown and described, pressure on the order of 3,000 pounds per square inch is applied to them and while so held they are soldered or welded together as indicated at Hi to provide a leak-proof assembly. Silver soldering has proven particularly satisfactory.

The following provision is made for the supply of fuel to the injector:

There is provided adjacent the lower end of I the upper shell H, but at a considerable distance from the sparking end of the plug, an annular conical seat 16 on which is positioned a slotted conical gasket 80, shown in detail in Figure 2. Seated on the gasket is a collar 82 provided washers I0, c-spring I and washers I2 and 14 with each other nor with nut 04, nor the assembly of nut 04 and Belleville washers I2 and washer It with each other nor with the hollow. center electrode are liquid tight so that fuel fills all the space within the pockets in the insulators and surrounds the hollow center electrode 2 and, of course, fills the spiral passages in the valve 40. The'washers referred to may be specially shaped to permit more ready passage of fuel as by provision of slots; in washer 12 as shown in Figure 3.

It will be apparent from following the course taken by fuel in its passage to the combustion chamber that a labyrinth has been provided with many pockets in which particles of dirt may be trapped and prevented from reaching the valve seat and interfering with its operation. Thus, with the plug in the position shown in Figure 1, the space surrounding the upper end of the lower insulator, and the space within the lower insulator below the washer I2 and above the gasket II, constitute sediment traps. With the plug inverted the interior of the upper insulator constitutes a trap.

The collar 02 is held tightly on its seat by means of nut 00 threaded on the upper shell. Nut 92, also threaded on the upper shell, serves both to connect the shielded cable to the shell and also looks the nut 00.

The construction described provides a sealed spark plug and injector unit which may be readily fitted to the engine and removed'therefrom by applying a wrench to the flatted portion 94 formed on the lower shell I2. Thereafter the fuel connections may be applied as described, followedby theconnection of the armored ignition cable in the usual manner.

Attention is particularly called to the factthat the portion of the upper insulator below the washer 00 and the portion of the lower insulator above the washers 24 and ii are immersed in fuel so that they are constantly being cooled by it. This makes it possible to use a long thin skirt on the insulator, as shown in Figure 1. Were cooling not provided the skirt would be likely to become incandescent in the operation of the engine and cause preignition of the combustible mixture. By its provision the spark plug is practically free from fouling or shortcircuiting as the result of deposit of lead or carbon on the insulator.

It will also be apparent that there is little opportunity for combustion gases to escape past leaky gaskets and foulthe plug or burn the connecting wiring inasmuch as the space behind each gasket is filled with fluid which is substantially incompressible. Should leakage develop there may be a slight s epa e of fuel into the combustion chamber which might interfere with combustion but there is no possibility of fire as in the case of conventional plugs.

The fuel likewise effectively cools the center electrode 20 thereby greatly increasing its life.

In actual operation the center electrode has successfully resisted erosion while the side electrode,

aesaaae 6 lacking provision for cooling, is eventually burned away.

Conventional spark plugs are sometimes shortcircuited by discharge of current taking place along the surface of the upper portion of the insulator instead of between the electrodes. With our improved plug having its interior filled with satisfactorily with a gap four times as great as the maximum permissible with conventional plugs.

In the modification shown in Figures 4 and 5 there is disclosed a shell consisting of a lower part I00 having its end threaded to fit the threaded opening in the engine cylinder; a central part I02 and an upper part I04. Within the lower part I 00 the insulator I06 is seated with the usual gasket interposed. Within the insulator there is secured the hollow center electrode I00 held In place by nut H0 in much the same manner as electrode 20 of Figure 1. The fuel injector valve H2 is slidably mounted within the hollow electrode. Spring III resting at its lower end on nut IIO yieldingly urgesv the valve toward seated position by engagement with nut IIB threaded on the upper end of the valve. Nut I25, also threaded on the valve stem, locks nut H0 in' position.

Insulator I00 is held in place by annular C-shaped spring I I 8 engaging a gasket surrounding the insulator shoulder and held in place in turn by the lower reduced portion I20 of the central shell member I02.

Seated on a gasket engaging the upper end of the center shell section I02 is the upper insulator I22. Within the center bore of the upper insulator is an electrode comprising a threaded portion I24; a conducting glass seal I26 which may, if desired, include a resistance similar to that indicated at 60 in Figure 1; and, embedded in the glass seal, contact member or cap I28 adapted to be engaged by the terminal of the lead-in wire. A light spring I21 of suitable heat resisting metal Isarranged as shown to conduct current from the threaded member I24 to the center electrode through nut II6. Lock nut 25 engaged by a shoulder formed in the upper shell member I04.

The parts described are assembled as shown in the drawing under heavy pressure so as to cause the springs H8 and I29 to be compressedsufilciently to make a gas and liquid tight assembly and while so compressed are permanently secured together as by silver soldering or welding as indicated at I32 and I34. Flatted portions I36 are provided on the lower shell member I 00 for engagement by a wrench to secure the plug in the cylinder.

I40 indicates a fitting for supplying fuel to the plug, in the form of an annulus surrounding the reduced upper portion of the shell member I04 and seating on a perforated gasket I42, as shown. The fitting I40 is provided with a radial tubular extension I44 adapted for connection with the fuel feeding pipe, and is held in place by nut I40 in threaded engagement with the upper portion of the shell section I04. Fuel ention I02 and thence downwardly and upwardly between the telescoping portions of the insulators to the helically formed. portion of the stem oi the valve H2 and thence through the hollow center electrode to the valve seat whence it may be discharged into the combustion chamber.

In the modified form of the device, if desired, the lower shell section I with its insulator may be assembled with the intermediate shell section It? and these parts may be welded together prior to applying the assembly including the upper in= sulator and shell section.

We claim:

1. In a spark plug, the combination of a cylindrical housing having axially spaced, apertured insulators therein, means for sealing the insulators in the housing, each of said insulators having a central bore, electrical conductors sealed in said bores, and an electrode secured to the housing at one end thereof cooperating with one of said conductors to form a spark gap, the other of said conductors having a resistance incorporated therein.

2. In a fuel injection spark plug the combina tion of a housing having an insulator therein, said insulator having a combination fuel in.- jector and electrode centrally secured therein, passages in said housing for supplying fuel to said injector and a cavity in said housing communicating with said passage but out of the line of flow therethrough for I trapping foreign particles therein.

3. In a fuel injection spark plug the combination of a tubular housing having inwardly extending shoulders adjacent its ends, insulators in the ends of the housing, each in sealing engagement with one of said shoulders, means common to said insulators yieldingly urging them into engagement with said shoulders, each of said insulators having a central bore, electrical conductors-in said bores, an electrode on one end of said housing cooperating with one of said conductors, the conductor in the other insulator w bore comprising a ceramic seal.

4. In a fuel injection spark plug the combination of a tubular housing having inwardly extending shoulders adjacent its ends, insulators in the ends of the housing, each in sealing engagement with one of said shoulders, means common to said insulators yieldingly urging them into engagement with said shoulders, each of said insulators having a central bore, electrical conductors in said bores, an electrode on one end of said housing cooperating with one of said conductors, the conductor in the other insulator bore comprising a resistance for reducing the sparking voltage.

5. In a fuel injection spark plug the combination of a tubular housing having inwardly extending shoulders adjacent its ends, insulators in the ends of the housing; each in sealing engagement with one of said shoulders, the adjacent ends of said insulators being'spaced from each other to provide a passage therebetween, means yieldingly urging the insulators into engagement with said shoulders, at least one of said insulators having a central bore, said housing being provided with an aperture therethrough communicating with the interior thereof between said shoulders and with the passage between said insulators, and a fuel injector mounted in said central bore and communicating with said passage.

6. In a fuel injection spark plug the combinatlon of a tubular housing having inwardly extending shoulders adjacent its ends, insulators in the ends of the housing, each in sealing engagement with one of said shoulders, the adjacent ends of said insulators being spaced from each other to provide a passage therebetween, means yieldingly urging the insulators into engagement with said shoulders, each of said insulators being provided with a central bore, said housing being provided with an aperture therethrough communicating with the passage between said insulators, a combination center electrode and fuel injector in one of said bores, an

electrode on the housing cooperating with said.

center electrode, and a conductor in the other of said bores in conducting relation with the said center electrode.

7. In a fuel injection spark plug the combination of a tubular housing having inwardly extending shoulders adjacent its ends, insulators in the ends of the housing, each in sealing engagement with one of said shoulders, the adja cent ends of said insulators being spaced from cash other to provide a passage therebetween, means common to said insulators yieldingly urging the insulators into engagement with said shoulders. one of said insulators having a central bore, said housing being provided with a passage therethroughv communicating with the interior thereof between said seals and with the passage between said insulators, a tubular electrode in the central bore of said insulator having its bore in communication with said last-named passage, and a spring-pressed valve in said electrode.

8. In a fuel injection spark plug the combination of an outer shell having an annular seat therein, an insulator in the shell having an annular shoulder in sealing engagement with the said seat, said insulator having a central bore, a tubular electrode sealed in said bore and having a seat for a valve therein adjacent its lower end, the interior of said tubular electrode being in open communication with the interior oi the shell, a valve having 'a stem loosely fitting said bore and a head in sealing engagement with the seat in the electrode; means yieldingly urging the valve into engagement with said seat, an apertured cover permanently secured to said shell, and spring means reacting between the insulator and cover urging the insulator into engagement with its seat, the periphery of said cover having an aperture therein, and a fuel supply conduit communicating with said aperture, and supply ing fuel therethrough to the interior of said electrode.

9. In a fuekinjection spark plug the combination of an outer shell having an annular seat therein, an insulator in the shell having an annular shoulder in sealing engagement with the said seat. said insulator having a central bore enlarged at its upper end to provide a pocket, a hollow electrode in said bore having a seat for a valve therein, the interior of said electrode being in open communication with said pocket, a valve having a stem loosely fitting said bore and a head in sealing engagement with the seat in the electrode,

means in said pocket yieldingly urging the valve into engagement with said seat, an apertured cover sesured to said shell, and spring means reacting between the insulator and cover urging the insulator into engagement with its seat, an aperture in said cover, and a fuel supply conduit communicating with said aperture.

10. In a combined fuel injector and spark plug the combination of a tubular housing, axially spaced insulators in said housing in sealing engagement with the ends of the housing, oneof said insulators having a central bore, a combined fuel injector and center electrode mounted in said bore, and means for supplying fuel to the interior of said housing and between said insulators to said injector.

11. In a combined fuel injector and spark plug the :ombination of a tubular housing, axially spaced insulators in said housing in sealing engagement with the ends of the housing, each of .said insulators having a central bore, a combined fuel injector and center electrode in one of said bores, a conductor in the other of said bores in conducting relation with the center electrode, and means connected to the exterior of said housing for supplying fuel to the interior of said housing and between said insulators to said injector.

12. A combined fuel injector and spark plug comprising a cylindrical housing, an insulator having an intermediate portion in sealing engagement with the housing, upper and lower portions of said insulator being spaced from the housing wall, said insulator having a central bore, a hollow center electrode secured in spaced relation in the lower end of the bore and having its lower end in sealing engagement with the lower end of the bore, a spring pressed fuel injection valve mounted in said electrode, means for sealing the upper end of said shell, and means for supplying fuel to the interior of said shell whereby fuel surrounds and cools the interior and exterior of the upper end of the insulator, the interior of the lower end of the insulator and the exterior of. the hollow electrode.

13. A combined fuel injector and spark plug comprising a cylindrical housing, an insulator having an intermediate portion seated in sealing engagement with the housing, the upper portion of said insulator being spaced from the housing. said insulator having a central bore, a combined fuel injector and center electrode secured in said bore, means for sealing the upper end of said shell, and means for supplying fuel to the interior of said shell whereby the fuel surrounds and cools the interior and exterior of the upper end of the insulator.

14. A combined fuel injector and spark plug comprising acylindrlcal housing, an insulator having an intermediate portion seated in sealing engagement with the housing, the lower portion of said insulator being spaced from the housing wall, said insulator having a central bore, a hollow center electrode secured in spaced relation in the lower end of the bore and having its lower end in sealing engagement with the lower end of the bore, a spring pressed fuel injection valve mounted in said electrode, means for sealing the upper end of said shell, and means associated with said housing for supplying fuel to the interior thereof and to said injector whereby the fuel fills the space between the hollow electrode and the insulator bore and cools the electrode and the insulator.

15. A spark plug comprising a cylindrical housing member having an annular shoulder provided with a conical face, a member encircling said shell and having a conical face cooperating with said first-named face to provide a leak-proof joint, means for clamping said members together, one of said faces having a concentric groove therein,

- each of said members having openings therethrough communicating with said concentric groove, and means for supplying fuel to the opening in said encircling member.

HECTOR RABEZZANA. FRANCIS J.- WIEGAND.

REFERENCES CITED The following references are of record in the nle of this patent:

I UNITED STATES PATENTS Number Name Date 1,333,897 Bringman Mar. 16, 1920 1,352,089 Schmidt Sept. 7, 1920 1,358,292 Collins Nov. 9, 1920 1,360,561 Mueller Nov. 30, 1920 1,430,964 Faber Oct. 3, 1922 1,525,083 Meyer Feb. 3, 1925 1,770,608 Fischer July 15, 1930 2,002,803 Tetlow May 28, 1935 2,008,803 Stephan July 23, 1935 2,173,766 Ramsay Sept. 19, 1939 2,238,397 Rabezaana Apr. 15, 1941 2,255,203 wa na Sept. 9, 1941 

